The production of veneers that are used in the manufacture of plywood is becoming more and more dependent on renewable resources, for example, logs used in the production of veneer come from reforested tree species. These reforested tree species are turning in logs of smaller diameter for the production of veneer. Thus, in order to be capable of producing veneer with lower costs and higher yields from log volume to veneer volume, there is a need for faster lathes which turn the wood logs to final smaller cores.
Standard lathes have fixed mechanical spindles located for gripping the ends of a log to be peeled, and the spindles rotate the log against a knife. The knife moves on a horizontal path and is indexed incrementally forward in a direction toward the log at a rate synchronized to the rotation of the log. The veneer is peeled off in a spiral manner from the log as the log is rotated against the knife. The amount of incremental forward movement determines the thickness of the peeled veneer. The spindles can be dual telescopic spindles on each end of the log or three telescopic spindles on each end of the log. These lathes can work with any shape and size of logs. However, the minimum diameter of the core remaining after the peeling of the log is finished is determined by the diameter of the smaller of the spindles in the dual or three telescopic arrangement.
There are also spindleless lathes which keep the center of rotation of the log in a fixed position, independent of the existence of mechanical spindles at the end of the log, and this arrangement allows the peeling process to continue to smaller core sizes. However, the disadvantage with this type of lathe is that it is only good for use with pre-rounded logs. In other words, the absence of mechanical spindles at the ends of the log requires that the outside surface of the log be cylindrical to allow adequate transfer of torque from the driving rollers to the log to thus peel veneer from the cylindrical log.
There are also mixed lathes which have single spindles on each end of the log during the initial portion of the peeling process. The spindles release the log when a certain diameter is reached. The peeling process continues after the release of the spindles by pure spindleless action as described above.
However, although standard lathes and mixed lathes can work with any shape of log and produce veneer down to a small core, they have the significant disadvantage of requiring a down time. During the down time, a new log is moved into position in the lathe so that it can be peeled. For example, when the peeling process reaches the core the lathe must be stopped, and the lathe knife carriage and associated counter rollers must be opened to allow for the introduction of a new log. Then, a separate apparatus brings the new log inside into the lathe machine. The mechanical spindles move in to grip both ends of the log, which is stationary, and then the apparatus is moved away to allow the spindles to start rotating the log against the knife, which will start indexing against the knife to peel the log and thus produce the veneer.
Thus, there is a significant need to eliminate the down time associated with presently existing lathes. There is also a need to increase the efficiency of the log peeling process.